Got the job offer...now what?

Leaving the Army and have hopefully just secured a job I’m very interested in. I was successful at interview and was phoned back with the job offer, then ended up being invited to a ‘chat’ to discuss terms and conditions of the role…Bit hung up about the dress code, I mean, I’ve got the job but I am still leaning towards a shirt & tie affair, just to keep appearences sweet…But several friends and family members think a more casual dress code would be fine…Any ideas?

Thanks a lot.